the rad flush should deal with it but the gunk might cause some problems to the cooling system if you use it.
you could have a look for the coloured hoses on ebay, you should be able to find some on there
Just buy some holts rad flush and it should clear all the rubbish out. The coolant on mine hadnt been changed for ages and i used that and it cleaned it all out. Then You'll be able to see if youve got a problem.